1985 2wd hatchback // 18 MPG - Please help

[applewew]

Hello,

I finally got the speedometer (thanks petros!) and therefore the mile counter on the car. It seems to be making 18 MPG which really sucks.

Any suggestions?

[Petros]

first of all, are you actually comparing miles per gallon, and not liters? Also, I wonder if the gear on your trans is the correct one for the speedo I sent you, you will have to check the actual distance driven against the odometer to verify. Use road signs, a GPS or even a good map to check distance between cities to check the odo on a longer drive.

Check your AAP, this will always eat lots of fuel, make sure your brakes are not dragging. Check your spark timing is correct (either with a timing light or adjust by "ear"; the most advance you can get without ping or crackle from the engine on hard acceleration). Verify your mechanical advance is working in the distributor. Check for vacuum leaks and misrouted vac lines.

Have you done a compression test on your engine? might help to know what kind of shape the internals of the engine are in.

good luck

[Mark]

I have an 83' 2wd hatchback and it gets worse fuel economy than my 4wd auto wagon in the city. Obviously something is wrong with it, but since it's just a backup vehicle for now, I'm not spending too much time on it. Also, on my hatchback, the trip counter is reading inaccurate. It sticks for longer than it should when the last digit is a "9". Sometimes it gets stuck until I reset it. If I was using that for my mileage calculations, the fuel economy would be REALLY bad. The odometer seems to be advancing fine so I use that for the calculations.

[applewew]

first of all, are you actually comparing miles per gallon, and not liters? Also, I wonder if the gear on your trans is the correct one for the speedo I sent you, you will have to check the actual distance driven against the odometer to verify. Use road signs, a GPS or even a good map to check distance between cities to check the odo on a longer drive.

I have double checked the odometer against road signs and the phone's GPS. Also made sure I'm talking about US gallons.

Check your AAP, this will always eat lots of fuel,

The AAP was recently placed during a carb rebuild.

make sure your brakes are not dragging. Check your spark timing is correct (either with a timing light or adjust by "ear"; the most advance you can get without ping or crackle from the engine on hard acceleration). Verify your mechanical advance is working in the distributor. Check for vacuum leaks and misrouted vac lines.

Have you done a compression test on your engine? might help to know what kind of shape the internals of the engine are in.

good luck

I will definitely check the timing, the mechanical advance and do a compression test. The vacuum lines were recently checked after finally getting the TVSV (thanks again)

[xirdneh]

tire air pressure?

[Mark]

I have an 83' 2wd hatchback and it gets worse fuel economy than my 4wd auto wagon in the city. Obviously something is wrong with it, but since it's just a backup vehicle for now, I'm not spending too much time on it. Also, on my hatchback, the trip counter is reading inaccurate. It sticks for longer than it should when the last digit is a "9". Sometimes it gets stuck until I reset it. If I was using that for my mileage calculations, the fuel economy would be REALLY bad. The odometer seems to be advancing fine so I use that for the calculations.

I guess what I was trying to say was: the trip counter and the odometer may not be travelling at the same speed. The trip counter may be reading too few miles/kilometers compared to the odometer.

[applewew]

tire air pressure?

Always at 35 PSI

[applewew]

I have an 83' 2wd hatchback and it gets worse fuel economy than my 4wd auto wagon in the city. Obviously something is wrong with it, but since it's just a backup vehicle for now, I'm not spending too much time on it. Also, on my hatchback, the trip counter is reading inaccurate. It sticks for longer than it should when the last digit is a "9". Sometimes it gets stuck until I reset it. If I was using that for my mileage calculations, the fuel economy would be REALLY bad. The odometer seems to be advancing fine so I use that for the calculations.

I guess what I was trying to say was: the trip counter and the odometer may not be travelling at the same speed. The trip counter may be reading too few miles/kilometers compared to the odometer.

I honestly don't know about the odometer, but I am sure the trip counter is working correctly, since its the one I compared with the road signs and gps.

[dlb]

here's my check list for common causes of poor fuel economy.

tire pressure
wheel alignment
extra cargo weight
ignition timing
air filter
dizzy rotor
dizzy cap
spark plug wires
spark plugs
vacuum leaks
correct vacuum routing
choke wide open once warm
AAP diaphragm
dragging brakes

is your hatchback an automatic or manual trans? when checking for vacuum leaks, test all the diaphragms on the vac advance, choke opener, choke breaker, throttle positioner, etc. if you can suck air through them, they are broken and a vacuum leak. disconnect and plug those lines until you can replace those components.

[applewew]

here's my check list for common causes of poor fuel economy.

tire pressure
wheel alignment
extra cargo weight
ignition timing
air filter
dizzy rotor
dizzy cap
spark plug wires
spark plugs
vacuum leaks
correct vacuum routing
choke wide open once warm
AAP diaphragm
dragging brakes

is your hatchback an automatic or manual trans? when checking for vacuum leaks, test all the diaphragms on the vac advance, choke opener, choke breaker, throttle positioner, etc. if you can suck air through them, they are broken and a vacuum leak. disconnect and plug those lines until you can replace those components.

It has a 5 speed manual trans.

Nice checklist, I will work through it.

[Petros]

It will not harm it to double check everything just to make sure. go from similest to more complex/more costly.

[applewew]

I will check and double check everything on the weekend, thanks guys, I'll keep you posted!

[dlb]

another thing i just thought of: the TVSV may be worn out, causing it to always supply vacuum to the AAP. remove and test it using the procedure on page 110 (EC-22) of the FSM.

if it is worn out, i know forum member 4doorvip found a few new ones that he was selling. i got one and it worked great. not sure if toyota still sells them, and most junk yard ones are broken or worn out.